Agents and N2O detection apparatus

ABSTRACT

A detector that monitors the presence of halogenated agents and the presence of N2O includes a base to which a filter cannister is removably coupled. The cannister has an input for accepting exhalent from a patient or an anesthesia machine and an outlet for outputting the filtered exhalent as gases to the base. The filtered gases are routed a gas measurement or monitor cell housed in the base. The cell has a halogenated agents sensing system and a N2O sensing system. When the filter material in the filter cannister could no longer filter out the halogenated agents, the agents are passed from the filter to the measuring cell, which would detect the presence of the halogenated agents. An audible alarm sounds when halogenated agents are detected. This tells the user that it is time to replace the filter cannister.

FIELD OF THE INVENTION

The present invention relates to detection of halogenated agents andgases used in an anaesthetic setting and more particularly to anapparatus for detecting the presence of halogenated agents and N2O(nitrous oxide).

BACKGROUND OF THE INVENTION

When anaesthetic gases are used in a hospital environment, such as forexample in an emergency or operating room, the halogenated agents fromthe gases or the exhalent of the patient have to be purged from theimmediate enclosed environment to protect the people in that enclosedenvironment. To achieve this purging of the halogenated agents, thepatient, and the anesthetic machine to which the patient most likely isattached, are connected to a scavenging system whereby the halogenatedgases are exhausted to the outside environment away from the enclosedoperating room. Oftentimes, N2O is also used in an operating room.

To remove the anesthetic gases from the exhalent of a patient, there hasbeen disclosed in the prior art the use of an adsorbent unit in the formof disposable cartridges (U.S. Pat. No. 3,941,573, U.S. Pat. No.3,867,936 and U.S. Pat. No. 5,044,363) in which the patient's exhalentis adsorbed. These disposable cartridges contain adsorbent fillers thatreact with and absorb the halogenated gases. As the amount of anestheticgases is absorbed, the material in the disposable cartridges orcontainers saturates and the cartridges would increase in weight and asa consequence will no longer adsorb the anesthetic gases after a giventime. Thus, after a certain amount of time or after the cartridges reacha certain weight, these cartridges are replaced with new cartridges.

There has also been disclosed in the prior art (U.S. Pat. No. 5,231,980)a process for recovering the halogenated hydrocarbons from a patient'sexhalent. To accomplish this, the '980 patent discloses the use of asensor at the exhaust line to sense the presence of anesthetics exitingfrom the cannister that adsorbs the halogenated hydrocarbons. The sensormay be connected by a signal line to the anesthesia machine to providean indication to the anesthetist that the adsorbent cannister should bereplaced so that the recovery of the anesthetics could continue. For thedevice disclosed in the '980 patent, the cannister has to be connectedto the anaesthesia machine by both a gas line and a signal line. Insofaras the cannister has to be connected to the anesthesia machine, it isconsidered as part of the anesthesia machine and accordingly iscumbersome and not meant for portability.

A need therefore exists for a portable standalone system that has areplaceable cannister adaptable for adsorbing halogenated agents. Theportable standalone system could be used in any environment, includingan enclosed room in which halogenated hydrocarbons may be released fromthe exhalent of a patient.

The present invention detection device is used where it is not possibleto vent the anesthetic gases directly into an operating room, sincedoing so would cause the air in the operating room to exceed OSHA limitsin a relatively short period of time, as for example 10 minutes in theinstance where the operating room is a small room in a field hospital,or a veterinary operating room where a veterinarian is treating ananimal.

SUMMARY OF THE INVENTION

The halogenated agents and N2O detection device of the instant inventionis a portable device that has a base housing to which a replaceablefilter device in the form of a cannister is secured. The cannistercontains materials that adsorb the halogenated agents from the exhalentof the patient that may be mixed with the anesthetic gases from ananesthesia machine. The patient's exhalent is input to the cannister,which is secured to a base housing in such a way that the outlet of thecannister is fitted to an input port at the base. The patient'sexhalent, after passing through the cannister and sucked through theinput port of the base, is further filtered by a contaminant filter.Thereafter, the filtered gases are routed to a measuring cell thatcontains a metal oxide semiconductor sensor and an optional opticalsensor. Halogenated agents that are not adsorbed by the agents adsorbentmaterial in the cannister are detected by the metal oxide semiconductorsensor, while N2O, which is not adsorbed by the material in thecannister, is detected by the optical sensor.

If halogenated agents are detected, an alarm, in the form of an audibletone, is output from the base housing to alert the user that thematerial inside the cannister is no longer adsorbing the halogenatedagents. An indicator, in the form of a light, on the display panel ofthe base, is also lit to inform the user that the cannister needs to bereplaced. If N2O is detected, an audible alarm is likewise output. Also,a light on the display panel of the base is lit to notify the user thatN2O is being detected. The user could then take the appropriate action,by either shutting down the N2O source or using the necessary exhaustsystem to purge the N2O from the enclosed environment. The exhalent fromthe patient, once sampled by and passes through the measuring cell, isfed to a blower that vents the air out of the base housing.

The instant invention therefore defines an apparatus for detecting atleast the presence of halogenated agents that comprises a base, a filterdevice removably coupled to the base, the filter device having an inletfor receiving exhaled air including halogenated agents from a patient oran anaesthesia machine and an outlet for outputting the filtered air.The base has an opening adapted to removably couple to the outlet of thefilter device for receiving the filtered air. The base further houses amonitor system for detecting halogenated agents, if present, in thefiltered air, and an alarm system for warning the presence ofhalogenated agents in the filtered air.

The present invention is also defined by an apparatus for filteringexhaled air having halogenated agents that comprises a filter containerhaving an inlet for receiving the exhaled air. The filter containercontains material adapted to adsorb a predetermined amount ofhalogenated agents and has an outlet for outputting air filteredthereby. The apparatus further includes a base having an opening foraccepting the outlet of the filter container, the outlet and the openingcooperating to non-permanently secure the filter container to the base.The base further houses a monitor system fluidly connect to the openingfor receiving the filtered air and adapted to detect halogenated agentsin the filtered air, and an alarm system electrically connected to themonitor system for outputting an alarm signal when halogenated agentsare detected in the filtered air. The alarm signal is removed when thefilter container is replaced by a new filter container.

The present invention is further defined by a method of monitoring airexhalent by a patient that comprises the steps of connecting the patientto a breathing device, and connecting the output of the breathing deviceto an input of a filter device, the filter device having an outletremovably connected to the base, the base housing a monitor system andan alarm system. The method of the instant invention further utilizesthe monitor system to sample and detect the presence of halogenatedagents in the air filtered by the filter device, utilizes the alarmsystem to output an alarm if halogenated agents in the filtered air aredetected by the monitor system, and replaces the filtered device whenthe output alarm is detected.

Another aspect of the instant invention is the detection of N2O from theexhaled air.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will become apparent and the invention itself willbe best understood with reference to the following description of thepresent invention taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is an assembled view of the device of the instant invention;

FIG. 2 is a perspective view showing the cannister portion beingelevated from the base portion of the device of the instant invention;

FIG. 3 is a plan view of the bottom of the cannister as shown in FIG. 2;

FIG. 4 is a perspective view of the bottom of the cannister of FIG. 2showing in particular the mechanism used to couple the cannister to thebase;

FIG. 5 is another view of the device of the instant invention with thecannister being separated from the base and the base semi-opened to showthe various components housed therein;

FIG. 6 is an exploded view of the various components housed in the baseportion of the instant invention device;

FIG. 7 is a different view of the various elements housed in the base ofthe instant invention;

FIG. 8 is yet another exposed view of the various components housed inthe base of the instant invention device;

FIG. 9 is a block diagram illustrating the power supply circuits forproviding power to operate the instant invention device;

FIG. 10 is a block diagram illustrating the circuits for operating thehalogenated agents sensor in the instant invention device;

FIG. 11 is a block diagram illustrating the circuits unique to the N2Osensor of the instant invention;

FIG. 12 is a flow diagram illustrating the operation of the processorthat controls the sensor that senses the halogenated agents; and

FIG. 13 is a flow chart illustrating the operation of the main processorof the instant invention device.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 14, the halogenated agents and N2O detectiondevice of the instant invention is shown to include a filter device inthe form of a cannister 2 and a base or housing 4. Cannister 2 isconfigured in a conical shape, with an inlet port 5 and an outlet port6. Stored in cannister 2 are activated charcoal or other materials thatare adaptable for adsorbing halogenated agents or hydrocarbons that arepart of the exhalent from a patient fed to the cannister via inlet 5.Some of the chemical materials that may be used are disclosed in thepatents discussed in the Background of the Invention as for examplethose disclosed in the '980 patent, the disclosure relating to thechemical materials being incorporated by reference herein. To preventthe activated charcoals, in the event that charcoals are used, fromfalling out of cannister 2, respective sponge filters are provided atthe inlet and outlet portions of the cannister. In regular use, thematerials in cannister 2 are adapted to adsorb halogenated agents forapproximately ten hours.

Outlet 6 of cannister 2 is configured to have two flanges 8a and 8b thatallow a user to non-permanently secure or couple cannister 2 to base 4,with outlet 6 being mated to input port 10 of base 4. Flanges 8 a and 8b act as a first half of a locking mechanism for securely couplingcannister 2 to a counterpart half of the locking mechanism at input port10 of base 4, when cannister 2 is rotated. To remove cannister 2 frombase 4, cannister 2 is rotated in a counter direction.

Base 4 has a display panel 12 that contains a number of indicator lightsdesignating “STATUS”, “AC PWR”, “LOW BATT”, “AGENTS”, “N₂O” and “ONOFF”. There are also two switches provided at the front panel. Switch 16is the on/off switch while switch 14 is a button that, if pushed, wouldsilence an audible alarm for a given period of time. A more detaileddiscussion of the various indicator lights will be given infra.

Base 4 is accessible via a door 18, shown in FIG. 5. Door 18 is openedby the sliding of a knob 20. A number of footpads 22 are provided at thebottom of base 4 to lift the bottom surface of base 4 away from the topof any surface upon which base 4 rests.

FIG. 5 shows the various components and systems being housed in base 4.One of the components is battery 23, which, by opening door 18, could beaccessed and replaced by the user. For the embodiment as shown, battery23 is a set of 3 replaceable and non-rechargeable batteries having atotal of approximately 4.5 volts.

For illustration simplicity, the various components housed in base 4 areshown to be freely standing without housing cover 24 in FIGS. 6, 7 and8. FIG. 8 illustrates in more detail input port 10 at the base 4 whichincludes a cup-shape flange 26 that has an opening 28 for receiving theair filtered from cannister 2 and output from its outlet 6. Connected tothe side of receiver port 26 at an opening (not shown) is a conduit ortube 28. With receiver port 26 removed from the illustrations of FIGS. 6and 7, it can be seen that tube 28, which is a conventional plasticstubing that is adapted to carry the filtered air, has at its other end abulkhead connector 30. A disposable contaminant filter 32 is removablycoupled to connector 30 at its one end and a twist lock connector 34 atits other end. Contaminant filter 32 is used to filter out particles anddusts that may flow from cannister 2, due to the possible degradation ofthe sponge filters or the breakup of the activated charcoals insidecannister 2.

Connected to twist lock connector 34 is a clear plastics tube 36 that inturn is connected to a tube or conduit 38. Tube 38 is a tubing that ismade of a moisture adsorbing material such as Nafion, which is amaterial similar to Gortex that allows moisture vapor to equilibrate.The purpose of tube 38 is to ensure that the humidity of the air beingsucked into measuring cell 40 to which it is connected at its other enddoes not cause any condensation inside the cell. The length of tube 38is designed to be of sufficient length to allow the moisture toequilibrate from the filtered air being routed or sucked into themeasuring cell 40. Tube 38 is shown to have a loop configuration.

With its input 42 connected to tube 38, the filtered air is routed intomeasuring cell 40. In brief, cell 40 is configured to have thebox-shaped dimension as shown, and includes a semiconductor sensor (FIG.10) that changes its conductivity when the presence of halogenatedagents is detected.

Also provided in measuring cell 40 is an optional N2O sensor that has aninfrared (IR) measuring cell housed in cell portion 44, and a lightsource 46. The light from light source 46 passes through a filter wheel,so that the IR receiver can sequentially measure the signals in- andout-of the N2O absorption bands.. If installed as an option, the gasesfrom the patient would first pass the N2O sensor, before it is detectedby the semiconductor sensor for halogenated agents.

The electrical connector to the semiconductor sensor is shown to beattached to a side of measuring cell 40, and is designated 48. A numberof pins from connector 48 are used for connection to a circuit board(not shown) that is placed underneath the standoffs 50 for measuringcell 40, as best shown in FIG. 7. Also shown in FIG. 7 is a cover 52that could be considered as part of measuring cell 40 and that is usedto cover the spinning wheel of the N2O sensor. Additional cover plates54 are provided on opposite sides of measuring cell 40. To these coversplates 54 the standoffs 50 are mounted.

The air and gas mixture sampled in measuring cell 40 is passed to anoutlet 45 to which a tube 58 connects it to a blower 60. The fan inblower 60 creates a negative pressure to suck the filtered air fromcannister 2 to base 4 for sampling and to vent the sampled air from base4 through an exhaust port 62 as indicated by directional arrow 64.

A safety switch or sensor 66 is provided at input port 26 and proximateto the mouth of the port where the outlet of filter cannister 2 isaccepted. The purpose of switch 66 is to detect whether cannister 2 isproperly coupled to base 4. When cannister 2 is properly inserted toinput portion 26, a flange at cannister 2 activates the switch. Ifswitch 66 does not detect cannister 2, i.e., the filter for thehalogenated agents is not attached, the system will not operate.

FIG. 9 is a block diagram illustrating the power supplies used in thedetection apparatus of the instant invention. With the disposablebattery 23, the detection apparatus of the instant invention is usablein both the AC and DC modes. The circuits that are used to provide thevoltages for the N2O sensor are designated 68 and 70 in FIG. 9. The 4.5volt battery cell is referenced 72 in FIG. 9, with the wall adapterproviding the AC power designated 74. The battery manager, designated76, determines which voltage, either AC or DC, is to be used. Thevarious inputs/outputs connected to battery manager 76, and designated78, are used for diagnostic purposes. A 5 volt boost regulator,designated 80, receives the input voltage from battery manager 76, andprovides the input voltage to a 3.3 volt linear regulator 82. Theregulated 3.3 volt is stepped down to a 2.5 volt reference voltage. A 5volt shutdown circuit 86 is used to turn the agent sensor on and off. Tointermittently turn the N2O sensor on and off to preserve energy, the3.3 volt linear regulator is relied upon. The controlling of the on andoff of the shutdown circuit 86 is by way of a PIC processor, as shown inFIG. 10, which will be described in further detail later. A 8-10 voltboost regulator 88 controls the running of the exhaust fan. In sum, anumber of output voltages are provided by the power supplies of thedetection apparatus of the instant apparatus.

FIGS. 10 and 11 illustrate the operation of the processors forcontrolling the sensing of the N2O sensor and the agents sensor. Withreference to FIG. 10, note that a sensor, designated 90, is used fordetecting the presence of halogenated agents. This sensor is a metaloxide semiconductor sensor manufactured under part number SB95 by theFiS Intelligent Sensors company and distributed by the Advanced SensorProducts company of Markham, Ontario. Sensor 90 outputs its signal to anagent sensor bias and control circuit 92, that conditions the signal andprovides the same via an input 94 to a processor 96. Processor 96 is aPIC processor specially designed by the Microchip company with theappropriate algorithms for detecting the presence of halogenated agentsand/or anesthetic gases from sampled gases. An output serial signal 98is provided from processor 96 as an optional serial signal tocommunicate concentration numbers representative of the detectedhalogenated agents. These serial communication concentration numbers maybe used in a display or other functions not associated with thedetection apparatus of the instant invention. A temperature sensor andbias circuit 100 provides temperature sensing and biasing for processor96. As noted earlier, the halogenated sensing system monitors thechemical changes of semiconductor sensor 90, in response to the sensingof presence of halogenated agents.

The circuits for the N2O detector are shown in FIG. 11. There, an IRdetector 102, having part No. BXP-15 (M) manufactured by the Cal-SensorsInc., of Santa Rosa, Calif., is connected to an IR signal controlcircuit 104. Also providing an input to signal control circuit 104 is adigital voltage control circuit 106 that is bidirectionally connected toa processor 108. Processor 108 may be a MSP430F147 or TMS430147processor made by the Texas Instrument company. IR detector 102 detectsthe light output from an IR lamp 110, which output is filtered by awheel, as represented by filter motor 112. Filter motor 112 controls thespeed of the filter wheel to compensate for the wear of the wheelbearings. The control of the intensity of IR lamp 110 is via lampcontrol circuit 114, in reaction to signals from processor 108. Thecontrol of the filter motor, and the wheel driven thereby, is via filtermotor control circuit 116.

In addition to providing control for the circuits of the N2O sensingsystem, processor 108 also controls various operations of the detectionapparatus. As shown in FIG. 10, the serial output 98 from the agentsensor processor 96 is fed to a voltage translator 118 and input toprocessor 108. Also connected to processor 108 bidirectionally is JTAGheader 120, which is a diagnostic port for a technician to test thefunctionality of processor 108. The display panel 12 shown in FIG. 1, isrepresented by the user panel circuit, and is shown to have six I/O LEDSand two button switches. The various LEDs and button switches areconnected electrically to processor 108, with the LEDs being driven byan LED driver circuit 122. The cannister safety switch, designated 66 inFIG. 8, is also connected to processor 108 and controlled thereby. A fanmotor 124, which is used to drive fan 60, is likewise controlled byprocessor 108. An audible alarm, driven by an audible alarm driver 126,is activated by processor 108, when either the presence of halogenatedagents or N2O is detected, as noted above. A number of additionaldiagnostics contacts, designated 128, are provided to processor 108. Anoptional user serial circuit 130 may also be connected to processor 108to provide the detection apparatus with the option of obtaining valuesfrom some other device. An optional thermistor flow sensor 132, and itscontrol circuit 134, may also be connected to processor 108 to controlthe flow of air through the system for preventing occlusion of thesystem.

FIG. 12 is a simple flow chart illustrating the operation of PICprocessor 96 that detects the presence of halogenated agents. Theprocess begins with step 140 in which diagnostics are performed on theprocessor and the status of the processor is displayed. The ambienttemperature is determined in step 142. Pulsed current is provided toheat the agent sensor and the prior adsorbed gas is purged, per step144. The current is then reduced to attain the operating temperature forthe sensor in step 146. The resistance of the semiconductor sensor isthen determined in step 148. The concentration of halogenated agents, ifany, detected by the sensor is obtained. The concentration of thehalogenated agents is then compared with a predetermined threshold orlimit. If the limit is exceeded, then it is assumed that halogenatedagents are detected. At which time audible alarm driver 126 isactivated. At the same time, the “AGENTS” LED on display panel 12 is litto inform the user that halogenated agents have been detected, per step152 of the process. To turn off the audible alarm for a predeterminedperiod of time, as for example 3 minutes, a user can press button 14located on the display panel 12. The operational process returns to step140 if no halogenated agents are detected, so that the stream of air fedto measuring cell 40 is continuously monitored.

FIG. 13 shows the operational process of main processor 108. Startingwith step 154, diagnostics are preformed by processor 108. Thereafter,per step 156, the various interrupts are tested and the appropriateoperations started. The interrupts are shown by the side flow charts asthe Period Real Time interrupt and the Comparator or Sampling interrupt.

For the periodic real time interrupt, designated 1560, the various flagsare set and prepared per step 1562. The state of the switch operable bythe user is read per step 1564. If there is an interrupt, the processreturns to its periodic operation per step 1566. For the comparator orsampling interrupt 1568, the A/D conversion of the pulse valuesoperation is performed in step 1570. The various levels of the pulsesare converted per step 1572, and the determination of the presence ofN2O is done per step 1574. And if the N2O concentration is determined tobe greater than a preset level, the “N2O” LED is lit on display panel 12and audible alarm 126 sounds. The interrupt then returns to await thenext interrupt request per step 1576.

Returning to the operation of processor 108, the fan operation iscontrolled per step 158. Processor 96 is activated intermittently tocontrol the sensing of the halogenated agents per step 160. The readingof the data from processor 96, the alarm/false status and the setting ofthe alarm flags are performed per step 162. Main processor 108 alsocontrols the operation of the N2O sensor and its various components viasteps 164 and 166. The setting of the test alarm flags and othermiscellaneous operations are performed by steps 168 and 170, whichoperations are as shown in those blocks.

1. Apparatus for detecting at least presence of halogenated agents,comprising: a base, a filter device removably coupled to said base, saidfilter device having an inlet for receiving exhaled air includinghalogenated agents from a patient or an anaesthesia machine and anoutlet for outputting the filtered air, said base having an openingadaptable to removably couple to the outlet of said filter device forreceiving the filtered air, said base housing a monitor system fordetecting halogenated agents, if present, in the filtered air, and analarm system for warning the presence of halogenated agents in thefiltered air.
 2. Apparatus of claim 1, wherein said monitor system isfurther adaptable for detecting the presence of N2O (Nitrous Oxide) fromthe exhaled air.
 3. Apparatus of claim 1, wherein said filter devicecomprises a cannister and wherein the outlet is removably matable withsaid opening of said base to securely mount said cannister to said base,halogenated agent adsorbent material being stored in said cannister foradsorbing the halogenated agents from the exhaled air.
 4. Apparatus ofclaim 3, further comprising a safety switch located proximate to saidopening at said base for detecting whether the outlet of said cannisteris securely mated to said opening of said base.
 5. Apparatus of claim 1,further comprising a display panel having thereon at least one indicatorresponsive to said alarm system for indicating the presence of N2O, andanother indicator for providing an alarm that halogenated agents are nolonger being adsorbed by said filter device.
 6. Apparatus of claim 1,wherein said base further houses a first conduit extending from saidopening to one end of a contaminant filter, said contaminant filterbeing replaceable and has its other end connected to a second conduitthat routes the filtered air to said monitor system for detecting thepresence of the halogenated agents and N2O.
 7. Apparatus of claim 6,wherein the filtered air sampled by said monitor system is thereafterrouted by a third conduit to an air blower housed in said base, saidblower venting the filtered air from said base to the environment.
 8. Amethod of monitoring air exhaled by a patient, comprising the steps of:connecting the patient to a breathing device; connecting the output fromthe breathing device to an input of a filter device, said filter devicehaving an outlet removably connected to a base, said base housing amonitor system and an alarm system; utilizing said monitor system tosample and detect the presence of halogenated agents in the air filteredby said filter device; utilizing said alarm system to output an alarm ifhalogenated agents in the filtered air are detected by said monitorsystem; and replacing said filter device when said output alarm isdetected.
 9. Method of claim 8, further comprising the steps of:utilizing said monitor system to detect the presence of N2O (NitrousOxide) in the filtered air; and outputting a N2O alarm if N2O isdetected.
 10. Method of claim 8, further comprising the step of: ventingthe filtered air from said base.
 11. Method of claim 8, furthercomprising the steps of: providing a switch proximate to an opening atsaid base whereto the outlet of said filter device is removably coupled,said switch detecting the coupling of said filter device to said base;and outputting an other alarm if said switch does not detect said filterdevice being coupled to said base.
 12. Method of claim 8, furthercomprising the steps of: providing at said base a display panel havingthereon at least one indicator responsive to said alarm system forindicating the presence of N2O, and another indicator for providing analarm that halogenated agents are no longer being adsorbed by saidfilter device.
 13. Apparatus for filtering exhaled air havinghalogenated agents, comprising: a filter container having an inlet forreceiving the exhaled air, said filter container containing materialadapted to adsorb a predetermined amount of halogenated agents, saidfilter container having an outlet for outputting air filtered thereby;and a base having an opening for accepting said outlet of said filtercontainer, said outlet and said opening cooperating to non-permanentlysecure said filter container to said base, said base housing a monitorsystem fluidly connected to said opening for receiving the filtered airand adapted to detect halogenated agents in the filtered air, said basefurther housing an alarm system electrically connected to said monitorsystem for working cooperatively with said monitor system to output analarm signal when halogenated agents are detected by said monitor systemin the filtered air; wherein said alarm signal is removed when saidfilter container is replaced by a new filter container.
 14. Apparatus ofclaim 13, wherein said monitor system is further adapted to detect thepresence of N2O (Nitrous Oxide), and wherein said alarm system outputs aN2O alarm when N2O is detected by said monitor system in the filteredair.
 15. Apparatus of claim 13, wherein said filter container comprisesa conical shaped cannister that has at the outlet a first connectingportion for non-permanently mating with a counterpart connecting portionat said opening of said base to secure said cannister to said base. 16.Apparatus of claim 13, further comprising a safety switch locatedproximate to said opening at said base for detecting whether said filtercontainer is secured to said base.
 17. Apparatus of claim 13, whereinsaid base further comprises a display panel having thereon at least oneindicator responsive to said alarm system for indicating the presence ofN2O, and another indicator for providing an alarm that halogenatedagents are no longer being adsorbed and said filter container needs tobe replaced.
 18. Apparatus of claim 13, further comprising an air blowerhoused in said base for accepting the filtered air from said monitorsystem, said blower purging the filtered air from said base to theenvironment.